There are two vital components to the kick serve. First and most importantly, you must contact the ball cleanly. Many people will tell you to brush up the back of the ball. While it looks like this is happening at normal speed, in slow motion you would see that contact is still pure, direct and cleanly right in the sweet spot. Second, you must let the ball drop further than a flat serve. You still must fully extend reaching up for the ball, but the contact is made just an inch lower than the flat serve.

twist

To get the twist, you gotta toss the ball so it would have landed behind you, back over your head, so your upwards and outwards swing gives it the right angle of top/sidespin component.
As said, you have to contact the ball LOWER than any other serve you do currently, so the racket can accelerate upwards during the contact.
Now back behind your head doesn't mean towards the backfence, but rather towards the SIDE fence, since on the trophy position, you are fully turned sideways or more.